1. Field of the Invention
This invention relates to shock actuated shut-off valves for fluid flow conduits and, more particularly, to a gastight reset system for such valves. In another aspect, this invention relates to the linear duplicate deployment of such valves wherein the internal orientation of one valve with respect to the internal orientation of the other valve is such that the valve system is actuatable over the broad potential direction of vibratory forces.
Although the shut-off valves described herein are particularly well adapted for closing natural gas lines in response to vibratory forces arising from seismic disturbances, their use is not so limited and they may be used to interrupt flow in lines carrying different kinds of gases and fluids under wide ranges of temperature and pressure in response to shock actuation from diverse sources.
In an earthquake or seismic disturbance of any significant magnitude, substantial vibratory forces are generated which can damage and rupture feeder lines used to deliver natural gas into residential, commercial and public structures. As a result, natural gas can leak or flow from such damaged or ruptured lines and accumulate in and about the aforesaid structures. The accumulated natural gas can form an explosive mixture with the surrounding area and be detonated by an appliance pilot light, other fire source or a spark. The fire and explosion hazard from damaged or broken gas lines following an earthquake is well known and constitutes a significant threat to persons and property.
A number of shock actuated, gas shut-off valves have been disclosed in the prior art to meet the fire and explosion hazard posed by earthquake damage to gas feeder lines. These prior art disclosures include U.S. Pat. No. 2,585,316 (Hobson, 1952); U.S. Pat. No. 2,927,592 (Ferre, 1960); U.S. Pat. No. 3,747,616 (Lloyd, 1973); U.S. Pat. No. 3,768,497 (Mueller, 1973); and U.S. Pat. No. 4,116,209 (Greer, 1978).
2. Prior Art
U.S. Pat. No. 4,116,209 discloses a shock actuated shut-off valve for fluid flow lines comprising: (i) a valve housing provided with a central chamber in communication with (a) a hollow inlet conduit, (b) a hollow outlet conduit, and (c) a hollow stowage arm in upward, substantially plumb communication with the central chamber, with the stowage arm being provided with closure means at its outer end; (ii) a valve element disposed in the stowage arm and having a valve body and valve head interconnected by a valve neck with the valve head being distal to the central chamber; (iii) a valve element support member secured to the inner wall of the stowage arm, with the valve head being in engagement with and releasably supported by the support member; and (iv) wherein the valve element is in spaced relationship to the surrounding inner wall of the stowage arm to thereby permit lateral displacement of the valve element from the support member and vertical transition of the valve element to the central chamber for sealingly engaging that chamber with respect to at least one of the inlet and outlet conduits.
In the prior art valve described in U.S. Pat. No. 4,116,209, the upper surface of the valve head is provided with a recess and a reset loop is mounted in the recess. Also, the lower portion of the housing, opposite the stowage arm, is distended to provide a lower level continuation of the central chamber. A threaded aperture traverses the distended portion of the housing and is sealingly engaged by a removable threaded plug. Reset is manually effected by removing the enclosure from the stowage arm and engaging the retrieval loop in the valve head with a suitably bent wire. The retrieved valve element is then manually returned to its releasably supported position in the stowage arm, and the closure re-assembled to the stowage arm. In the event that the valve element becomes tightly wedged in the closed position, the bottom plug can be removed and the valve element tapped out of its wedged position with a suitable instrument.
The aforesaid reset system, which requires the removal of the external closure from the stowage arm in order to gain access to the retrieval loop in the head of the valve element, exposes the inlet conduit and the central chamber to the surrounding environment which could present a hazard through the release of any gas to such environment.